1. Field of the Invention
This invention relates to a cleaning apparatus for cleaning the surface of the image bearing member of an image forming apparatus such as a printer, a copying machine or a facsimile apparatus.
2. Related Background Art
As a cleaning apparatus provided in an image forming apparatus such as a printer, a copying machine or a facsimile apparatus, there is known one having a cleaning blade as a cleaning member for cleaning an image bearing member.
For example, in an image forming apparatus adopting an electrophotographic process, a toner image is formed on a photosensitive drum (image bearing member) by way of image forming processes such as a charging process, an exposing process and a developing process, and this toner image is transferred from the photosensitive drum onto a recording material (e.g. paper) and an intermediate transferring member (a belt or the like) by a transferring process. In this transferring process, a toner constituting the toner image on the photosensitive drum is not all transferred to the recording material, but a small amount of toner is residual on the surface of the photosensitive drum (this also holds true in the case of the intermediate transfer member to the paper). The toner residual on the surface of the photosensitive drum (hereinafter referred to as the “residual toner”) in this manner is removed by the aforementioned cleaning blade.
In recent years, electrophotographic apparatuses have also been strengthening the tendency toward coloring and at the same time, toward a smaller apace and a lower cost. On the other hand, in spite of higher performance being required of a cleaning blade, it is popular to contrive to meet the required performance by a fixed method using only a cleaning blade without using conventional cleaning auxiliary members (such as a spring, an equalizer, a reciprocator and a fur brush).
As a method of fixing the conventional cleaning blade, there is generally known a centrifugal forming method of making rubber into a strip and adhesively securing this to a metal plate, as what can cope with various materials and moreover, can realize a lower cost (see, for example, Japanese Patent No. 3087230).
In a case where as described above, the strip-shaped rubber is adhesively secured to the metal plate to thereby fix the cleaning blade, if the blade is brought into contact with the drum for a long period, there will arise the problem that even if the blade is spaced apart from the drum, the shape of the blade does not recover the original shape, but remains permanently deformed into the curved shape when the blade was in contact with the drum (hereinafter referred to as the squat). If the blade is thus permanently deformed, it will become impossible to apply pressure necessary for cleaning to the photosensitive drum, thus resulting in faulty cleaning. The main cause of this has generally been said to be the influence of an adhesive agent layer (see, for example, Japanese Patent Application Laid-open No. 2001-75452).
Also, Japanese Patent Application Laid-open No. S60-12569 discloses that in a cleaning apparatus wherein a blade and a holding member for supporting the blade are adhesively secured to each other, the distal end surface of the holding member and that surface of the blade which is adjacent to the holding member are secured to each other by an adhesive agent in order to prevent the blade from peeling from the holding member. It also describes that as the adhesive agent, use may be made of a rubber-like adhesive agent or an adhesive agent of a hardening type such as urethane.
However, regarding the problem of the squat of the cleaning blade in the case where the strip-shaped rubber is adhesively secured to the metal plate to thereby fix the cleaning blade, it has been found that the cause of the problem is not only the influence of the adhesive agent layer, but the influence of the construction of the cleaning blade is greater. That is, it has been found that when pressure is applied to the distal end of the cleaning blade, stress becomes a fulcrum at the point of contact between the metal plate and the rubber portion, and by that force, squat is caused to the cleaning blade. Also, in the construction of Japanese Patent Application Laid-open No. S60-12569, the blade is held by being adhesively secured to the holding member, but the adhesively secured surface between the blade and the holding member is held from that surface of the plate-shaped blade which is adjacent to the drum (the outer side of the cleaning apparatus). Thus, no elastic member is provided in a direction in which the distal end of the blade is deformed when the blade contacts with the drum and therefore, the squat cannot be prevented by the adhesive agent provided on the distal end portion of the holding member. Also, this publication lacks the detailed description of the specific shape and physical property value of the adhesive agent provided on the distal end portion of the blade holding member, and does not disclose specific description for preventing the squat of the blade as in the present invention. Also, the adhesive agent provided on the distal end of the holding member is a liquid-like (rubber-like) adhesive agent hardened. Therefore, it is difficult to secure the accuracy of the shape of the adhesive agent, and this leads to the problem that depending on the shape of the adhesive agent, the cleaning property is lowered.
Also, in a case where with various requirements taken into account, various rubber materials are used for the cleaning blade, the use range of the rubber materials is limited in the case of a construction in which the influence of the adhesive agent must be considered.